The
earliest surviving sundial is located in the Egyptian museum in Berlin,
with the catalog number 19744. Probably, it was found in Eschmunein. It
dates from the reign of Thutmosis
III (1479 - 1425 BC) during the New Kingdom. The name and
titles of the pharaoh are engraved on the side

It is made of stone (schist) and is shaped like the
letter L. The short piece is the gnomon (vertical rod giving a shadow).
In the gnomon there is a hole for attaching a small
plumb bob. Below is a vertical groove to align the thread
of the plumb bob.

In the horizontal plane of the long bar there are five circles as marks
of a time scale. The distances between the marks are proportional to the
numbers1,2,3,4,5.

Photo: Website Verein zur Förderung des
Agyptischen Museums Berlin

The hypothesis of Ludwig Borchardt
and
Evert Bruins

In
1910 the German Egyptologist Ludwig Borchardt formulated the hypothesis
that the shadow of the gnomon gives an indication of the so-called unequal
hours on the time scale.

Those divide the
period between sunrise and sunset into twelve equal parts.
Because in wintertime the period between sunrise and sunset is shorter
than in summertime, the hours, so determined, are unequal in length
depending on the season. Unequal hours were in use until the Middle
Ages.

The height of the sun varies also with the seasons and hence the length
of the shadow. To give a shadow to the correct mark in every season,
the gnomon should be variable in height. Therefore Borchardt assumed that
the sundial, as it was found, is incomplete.

Adapted to the season, a
crossbar of a suitable height had to be added, in his
hypothesis. In the course of history these crossbars were lost.

In the morning, the sundial was facing with the gnomon to the east and
at noon it
had to be turned with the gnomon to the west.

In 1965 the Dutch mathematician Evert
Bruins
calculated the shadow of a higher gnomon. He checked whether, given an
exact indica¬tion at a certain mark, the reading at the other
marks
are also correct. His finding was that the time keeping, as assumed by
Borchardt and tested with a graphical method, was a good
approximation
of the measurement of the unequal hours.

The L-shaped sundial fitted with a crossbar
as L. Borchardt drew him (a hypothesis rejected by Sarah Symons)

In 25 out of 229 pages she examined the L-shaped sundials and rejected
the theories of Borchardt and Bruins. For this she used her knowledge
of Egyptian texts and culture and the mathematical background of
gnomonics.

In passing, she pointed out that the
obelisks at the temples were not
intended as a sort of sundial. There was surely a
connection with the sun and the cult of the sun. The high peak of an
obelisk, covered with an alloy of gold and silver, reflects the sun
before sunrise. The main function of an obelisk was, according to its
engravings, to serve as a memorial in honour of the pharaoh to whom it
was devoted.

Only when obelisks later were moved to Rome and Paris later on, they
were used as a sundial.

Sarah Symons refutes
Borchardt’s theory about the ancient Egyptian
L-shaped sundial based on four arguments:

1. The
text in the cenotaph named Osireon

In
the cenotaph, named Osireon,
near the temple of Seti I at Abydos there is a text on a ceiling that
describes the construction and usage of such L-shaped sundials.

In the text and on the accompanying drawing, there is no mention of a
crossbar, only of the
L-shape.

The simple ratios of the distances between the marks are indicated as
corresponding to 3, 6,
9, 12. As in other ancient Egypt drawings, the distances
are not drawn to scale. The text describes these relations as "an
established procedure.”

The passage in the text on the orientation of the sundial can be
interpreted in two ways: an east-west orientation with a
rotation of 180 degrees at noon or a continuous turning towards the
sun.

The
figure in the Osireon text with the distances between the markings
indicated as ratio's 3, 6, 9, 12.

2. The
sundial hieroglyph

Among
other characters the Egyptian used logograms. These are characters
whose form refers to the concept it stands for. The sign for "sundial"
is such a logogram. It shows the L-shape with a small plumb bob,but
a crossbar cannot be seen.

Later developments in the shape of the sundial are always shown in
logograms. There is never a crossbar image.

The hieroglyph for sundial: the shape refers to the concept it stands
for,
the L-shaped instrument with the little plump bob.

3. The
calculation of the indications of unequal hours

Bruins
calculated the length of the
shadow for a given (unequal) hour – in this case
the 10th or the 2th hour - at the winter solstice, the equinoxes and
the summer solstice.

For each of these moments he calculated a crossbar of suitable height
so that the shadows have the same length and reach the mark of the
chosen unequal hour.
Then he calculated for those crossbars the length of the
shadows of other (unequal) hours and compared them with
the distances to the corresponding marks, determined by the ratios
indicated in the Osireon figure.

He deduced from the differences that there was a 'good
approximation' of the measurement of the unequal hours.

In the figure beside the results of the calculations, after
recalculation (see below), are converted in a drawing.

Sarah Symons also recalculated the shadow lengths. It is clear, she
concludes from the percentage errors, especially for the shortest and
longest shadows, that the
unequal hours are not measured with a degree of accuracy
that merits the addition of a crossbar.

4. The
usage of the sundial..According
to the hypothesis of Borchardt the sundial should have an east-west
alignment, in the morning with the gnomon to the east and rotated in
the afternoon to the west. This requires
an external reference for the cardinal directions, which
is not always available for this ‘portable’
instrument.

The only tool to set up the sundial, is the plumb bob to level it.
Directing the sundial with
the gnomon towards the sun
- the shadow coinciding with the long part of the L-shape over its full
width - is the obvious method of use, to carry out without tools.

Moreover, it is consistent with the Osireon text: "Then
the shadow of the sun will be aligned on this instrument”.

Conclusion
Sarah Symons' conclusion is: the simplest, most obvious and most easily
supported
theory is that the sundial is an
L-shaped instrument which is portable and can b
used in any place marking
certain time periods. Alignment is provided by levellin
it using a 'built in' plumb bob and pointing the device towards the sun.

The simple relationship between the marks is a
convenient 'rule' for making a sundial
rather than an accurate measure for unequal hours.

Adding a crossbar is a clever idea, but sprang from the
need to impose modern
insights about equally divided time periods to the time keeping in
antiquity.

Francis Maddison and Turner Anthony talk about "the over-sophisticated theory
of L. Borchardt and the wild fantasies of E. Bruins " versus
“the
most recent
- and correct - discussion of Sarah Symons”.

Eleven years ago Sarah Symons threw a new light on the oldest surviving
sundial.
Isn’t it about time to correct the description of the sundial
in numerous Internet
publications, especially in the catalog of the Egyptian
Museum
in Berlin.